To meet the demand for wireless data traffic having increased since deployment of 4G communication systems, efforts have been made to develop an improved 5G or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a ‘Beyond 4G Network’ or a ‘Post LTE System’. The 5G communication system is considered to be implemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higher data rates. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques are discussed in 5G communication systems. In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud Radio Access Networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), reception-end interference cancellation and the like. In the 5G system, Hybrid FSK and QAM Modulation (FQAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as an advanced access technology have been developed.
The Internet, which is a human centered connectivity network where humans generate and consume information, is now evolving to the Internet of Things (IoT) where distributed entities, such as things, exchange and process information without human intervention. The Internet of Everything (IoE), which is a combination of the IoT technology and the Big Data processing technology through connection with a cloud server, has emerged. As technology elements, such as “sensing technology”, “wired/wireless communication and network infrastructure”, “service interface technology”, and “Security technology” have been demanded for IoT implementation, a sensor network, a Machine-to-Machine (M2M) communication, Machine Type Communication (MTC), and so forth have been recently researched. Such an IoT environment may provide intelligent Internet technology services that create a new value to human life by collecting and analyzing data generated among connected things. IoT may be applied to a variety of fields including smart home, smart building, smart city, smart car or connected cars, smart grid, health care, smart appliances and advanced medical services through convergence and combination between existing Information Technology (IT) and various industrial applications.
In line with this, various attempts have been made to apply 5G communication systems to IoT networks. For example, technologies such as a sensor network, Machine Type Communication (MTC), and Machine-to-Machine (M2M) communication may be implemented by beamforming, MIMO, and array antennas. Application of a cloud Radio Access Network (RAN) as the above-described Big Data processing technology may also be considered to be as an example of convergence between the 5G technology and the IoT technology. Meanwhile, an LTE system may determine whether to perform application-specific access barring and control accesses per application. However, the complicating application-specific access barring mechanism gives rise to the necessity of a consistent access control mechanism.
Meanwhile, with two DRX cycles (long DRX cycle and short DRX cycle) specified in LTE standard, it may be impossible to adjust the DRX cycle dynamically according to Data Radio Bearer (DRB) characteristics, traffic pattern, and buffer status. Thus, there is a need of a method for adjusting the length of the DRX cycle efficiently.
In LTE, a new operation mode, called light connection mode, has been proposed to define a state where a base station (evolved Node B: eNB) and a terminal (User Equipment: UE) maintain the UE information (e.g., context information) even when the connection therebetween is disconnected in addition to the idle mode and the connected mode. In an LTE system, if the tracking area of a UE in the light connection mode is changed, the UE may transition to the connected mode and transmit a tracking area update message to the core network. This means that the UE has to transition to the connected mode despite no data to transmit.
For next generation mobile communication systems, it may be considered to use Ultra Reliable (packet error rate of 10-5) Low-Latency Communication (URLLC) services. Examples of the URLLC services may include an automated vehicle service, an e-health service, and a drone service. In the LTE system, the negative acknowledgement (NACK) corresponding to a packet transmission trigger retransmission and thus may cause transmission latency. There is therefore a need of specifying detailed operation for retransmitting URLLC service packets efficiently.
In a case where a UE is handed from one eNB to another in the LTE system, the UE cannot communicate data with the network during a period between the time point when it receives a handover command message from the source eNB and the time point when the UE transmits a handover complete message to the target eNB. Here, the period during which data transmission is impossible is called data interruption time. Typically, the data interruption time lasts at least a few dozen ms, resulting in data cutoff. Thus, there is a need of a method for minimizing the data interruption time.
In a network supporting the light connection mode, the UE in the idle mode may report UE location on the move in the paging area configured by the network. In this case, a large amount of signaling is required between the UE and the eNB in order for the UE to transition to a large paging area preference mode for battery power saving.
Also, in the case that the UE stays in the light connected mode for a long time, the network has to store and maintain the UE context and S1-U bearer information. This means that the network cannot manage the UEs in the light connected mode continuously but controls them to transition to the RRC Idle mode. This operation for transitioning the UE operation mode from the light connected mode to the RRC Idle mode may cause significant signaling overhead.